1. Hydrolysis reaction: Methyl 4-cyano-2-methylbenzoate (38g, 0.217mol) was dissolved in ethanol (450ml), aqueous sodium hydroxide (150ml, 2.9M) was added slowly, and the reaction was stirred for 12 hours at room temperature. After completion of the reaction, most of the ethanol was removed by distillation under reduced pressure. The residue was diluted with distilled water (300 ml) and the aqueous layer was washed with ether (200 ml x 2) to remove organic impurities. Subsequently, the aqueous layer was acidified with hydrochloric acid (450 ml, 1 M) to pH < 6 at 0 °C. The acidified mixture was extracted with ethyl acetate (400 ml × 3), the organic layers were combined, washed with saturated brine, dried with anhydrous sodium sulfate, and concentrated under reduced pressure to give 4-cyano-2-methylbenzoic acid (40 g, 100% yield), the product was a yellow solid.
2. Acetylation reaction: 4-cyano-2-methylbenzoic acid (20g, 0.124mol) was dissolved in toluene (200ml), thionyl chloride (18ml, 0.248mol) and catalytic amount of dimethylformamide (0.5ml) were added. The mixture was stirred at 70°C for 14 hours. At the end of the reaction, the solvent and excess reagents were evaporated under reduced pressure to give 4-cyano-2-methylbenzoyl chloride (24 g, 100% yield), which was used directly in the subsequent reaction without further purification.
